Process for preparing 2-hydroxyalkylphosphines and 2-hydroxyalkylphosphonium salts



United States Patent 0 3,251,883 PROCESS FOR PREPARING Z-HYDROXYALKYL- PHOSPHINES AND Z-HYDROXYALKYLPHOS- PHONIUM SALTS Michael M. Rauhut, Norwalk, and Andrew M. Semsel, Stamford, Comm, assignors to American Cyauamid Company, Stamford, Conn., a corporation of Maine No Drawing. Filed July 20, 1962, Ser. No. 211,412 11 Claims. (Cl. 260-6065) The present invention relates to organophosphorus compounds and to the preparation of same. More particularly, the present invention relates to 2-hydroxyalkylphosphines and 2-hydroxyalkylphosphonium salts.

Pursuant to the instant discovery elemental phosphorus is brought into reactive contact, in the presence of an inert organic solvent, such as an ether, with an organometallic compound of the formula RM wherein R is alkyl having from 1 to 12 carbon atoms, cycloalkyl, aryl and substituted aryl, typical substituents for aryl being halogen, lower alkoxy, trifluoromethyl, and the like. M represents Li, Na or MgX where X is Cl, Br or I. The organometallic solution is conveniently prepared in the conventional way from the metal and the corresponding aryl alkyl or cycloalkyl halide. Of course, when M is sodium or lithium the organometallic solution also contains the corresponding metal halide (X), which is the source of halide ion found in the phosphonium salt products. For instance, see Examples I, II, VI, etc., infra.

The product resulting from the reaction of elemental phosphorus and the organometallic compound is, in turn, brought into reactive cont-act with an oxide of the formula in which R represents hydrogen, alkyl having from 1 to 12 carbon atoms and phenyl, and the product from this reaction is hydrolyzed using water alone or, preferably, a dilute aqueous acid. The corresponding Z-hydroxyalkylphosphonium salt and Z-hydroxyalkylphosphine result, the latter generally being characterized and isolated, as will be seen hereinafter, by furtherl reaction with, say, an alkyl bromide or iodide to obtain the corresponding phosphonium salt.

The following equation best illustrates the reaction and reaction products contemplated herein:

R"Z stands for lower alkyl bromide, lower alkyl iodide, allyl chloride, allyl bromide, benzyl chloride benzyl bromide, R" representing the organic moiety and Z representing the halogen moiety.

Each of the four reaction steps in the above equation is best carried out at a temperature in the range of 0 C. to 150 0., preferably 5 C. to 75 C.

Typical substituted or unsubstituted, monoand di-nuclear aryl lithium, magnesium and sodium compounds, substituted or unsubstituted, alkyl (C -C lithium, magnesium, and sodium compounds, and cycloalkyl lithium, magnesium and sodium compounds within the purview of the instant invention are: n-butyllithium, n-butylmagnesium bromide, n-butylmagnesium chloride, methylmagnesium iodide, pentyl sodium, methylmagnesium chloride, l-naphthyllithium, 3-(tiifluoromethyl)phenyllithium, 4- fluorophenyllithium, 4-methoxyphenyl1ithium, octylmagnesium bromide, heptyllithium, hexylmagnesium bromide, cyclohexyllithium, n-dodecyllithium, heptafluoropropyllithium, 6 methoxy Z-naphthyllithium, n propyllithium, 4-tolyllithium, 4-chloropheny1lithium, and the like.

Obviously, from the above list of organometallic compounds, the metallic. moiety may or may not be halo- 9 genated. Likewise, the organic moiety may or may not be substituted. Typical substituents for the organic moiety are those which under the conditions of the reaction contemplated herein are inert: halogen, such as fluorine and the like, lower alkoxy, such as methoxy, ethoxy, propoxy and butoxy, and like substituents.

The elemental phosphorus reactant may be employed, as indicated hereinabove, as a finely-divided white phosphorus. However, elemental phosphorus in a different physical state, such as molten phosphorus or phosphorus in the form of chunks, or other similar fractions, may be employed.

The reactants in the first two reaction steps, above, are best brought together in the presence of an inert organic solvent, i.e., a solvent which under the conditions of the reaction described herein does not react to any substantial degree with the reactants. Typical inert solvents are ethers, aromatic hydrocarbons, and the like, such as the following: tetrahydrofuran, diethylether,. benzene, toluene, xylene, dimethoxyethane, diethylether of diethyleneglycol, dioxane. In addition, aliphatic and. cycloaliphatic hydrocarbons are suitable solvents, such as pentane, decane, cyclohexane, etc.

The reaction step involving R"Z is likewise generally carried out in the presence of inert organic solvents of the typejust given for steps one and two.

As to the ratio of reactants generally employed, at least 0.5: 1, organometallic reactant to phosphorus atom, is em- 3 ployed; preferably a ratio of about 121 up to about 3:1 is

used.

Hydrolysis of the reaction mixture resulting from the second step of the process contemplated herein is carried out by conventional means using water, acetic acid or dilute mineral acid, such as dilute HCl, H SO etc.

The amount of oxide reactant introduced into the second of the above process steps is not critical. Preferably, however, an equimolar amount of oxide, such as propylene oxide, based upon the amount of organometallic reactant (of the first step), is generally employed. Substantially more or substantially less than an equimolar amount may be employed, however, without altering the nature of the reaction. This applies to the hydrolysis step as well as to the ratio of RZ reactant to organometallic reactant. In this later case, an equimolar amount of RZ reactant, based upon the amount of organometallic reactant, represents an excess of said RZ reactant over the intermediate The process of the present invention, including each reaction step, may be carried out at atmospheric, sub- 4 atmospheric, or super-atmospheric pressure. Batch, continuous or semi-continuous conditions may be employed.

The present invention will best be understood from the following typical examples:

EXAMPLE I Diphenylbis(2 hydroxypropyl)phosphonium bromide .Methyldiphenyl-2-hydr0xypr0pylphosph0nium iodide White phosphorus (15.5 grams, 0.5 gram atom) is combined with a solution of 1 mole of phenyllithium in 700 milliliters of ether under nitrogen. The mixture is stirred at reflux for 3 hours and allowed to cool to room temperature. A solution of 58.1 grams (1.0 mole) of propylene oxide in 50 milliliters of ether is added dropwise during 45 minutes at 25 C.-30 C. The reaction is strongly exothermic and requires cooling. The color changes sharply from dark red to pale yellow at the end of the addition. The reaction mixture is stirred an additional 30 minutes and then treated dropwise with 66.0 grams (1.1 moles) of glacial acetic acid, followed by the addition of 400 milliliters of water. The mixture is filtered to obtain 28.2 grams (15%) of diphenylbis(2-hydroxypropyl)phosphonium bromide, melting point 183 C.-187 C. The solid is washed with hot chloroform and recrystallized twice from isopropyl alcohol to obtain an analytical sample, melting point 197 C.200 C.

Analysis.Ca1culated for C H BrO P: C, 56.41; H, 6.31; Br, 20.85; P, 8.08. Found: C, 56.45; H, 6.46; Br,

The two liquid phases present in the filtered reaction mixture are separated, and the organic (ether) phase is dried over anhydrous sodium sulfate Concentration of the aqueous phase gives an additional 6.9 grams (4%) of diphenylbis(2-hydroxypropyl)phosphonium bromide, melting point 191 C.194 C.

The dried organic '(ether) phase is combined with 85.2 grams (0.6 mole) of methyl iodide, and the solution is refluxed for minutes. An insoluble oil separates. The ether phase is decanted, and the oil is stirred with milliliters of isopropyl alcohol. The oil crystallizes, and the resulting solid is collected to obtain 35.9 grams (19% of methydiphenyl-2-hydroxypropylphosphonium iodide, melting point 159 C.-162 C. Two recrystallizations from isopropyl alcohal give an analytical sample, melting point 163 C.164 C.

Analysis.Calculated for C H IOP: C, 49.75; H, 5.21; I, 32.86; P, 8.02. Found: C, 49.53; H, 5.16; I, 32.74; P, 8.14.

The phenyllithium reactant hereinabove is prepared in the conventional way from '1.0 mole of bromobenzene and 1 gram atom of lithium metal. The by-product lithium bromide from this preparation is the source of the bromide ion found in the diphenylbis-(2-hydroxypropyl)- phosphonium bromide.

EXAMPLES II-XXVII' The following table contains examples carried out'essentially as in'Example I, except as shown:

TABLE I.-ont1lmted OH Molar R OH Example Temp. Ratio 63 l l 9 No. [RzPCHr-CHR'] +RZ R POl'ICHIV-Z C. RZ P II Dibutyl-2-hydroxyethylphosphine Methyl iodide 0.5:1 Dihutylmethyl-Z-hydroxyethylphosphomum e. III Dibuty1-2-hydroxypropylphosphine Ethyl bromide 0.3:1 Dibutylgthyhg-hydroxypropylphosphomum lOIlll e. IV Dibutyl-2-hydroxybutylphospl1ine Methyl iodide 1:1 Dibutylpriiplyl-2-hydroxybutylphosphon1um1o 1 e. V Dimethy1-2hydroxy-2-phenylethylphos- ..d0 0. 7:1 Trimethyl-2hydroxy-2-phenylethylphosphine. phonium iodide. VI Dipentyl-2-l1ydroxy-2-phenylethylphos- Allyl chloride 1:1' Allyldipentyl-2-hydroxy-2-phenylethy1phosphine. phonium bromide. VII Didodecyl-2-hydroxyethylphosphine Methyl iodide 1:1 Didodeeylimtfthyl-zhydroxyethylphospho- I 1111111110 1 e. VIII Di-l-naphthyl-zhydroxypropylphosphine.. do 0.4:1 Di-ll-naphthylingathyl-2-hydroxy'propylphosp onium 1o 1 e. IX Bis[3-(triflnoro1nethyl)phenyl1-2-hydroxy- Propyl bromide 1:1 Bis[3-(triilnoromethyl)phenyl1-propyl-2- propylphosphine. hydroxypropylphosphonimn bromide. X Bis(4-Iluoropheny1)-2-hydroxypropylph0s- Ethyl bromide 1:1 Bis(4-fluorophenyl)ethyl-Z-hydroxypropylphine. phosphonium bromide. I XI Bis(4-methoxyphenyl)-2-hydroxypropyl- 2,4-diohlorobenzyl 1:1 Bis(4-methoxyphenyl)2,4-diehlorobenzyl-2- phosphine. bromide. hydroxypropylphosphonium bromide. XII Dioctyl-Z-hydroxypropylphosphine Benzylohl0ride-. 0.6:1 Benzyldioetyl-2-hydroxypropylphosphonium bromide. XIII Diheptyl-Z-hydroxypropylphosphine 0.9:1 Benzyldiheptyl-Z-hydroxypropylph0sphonium chloride. XIV DiheXyl-2-hydroxypropylphosohine Ethyliodide 1:1 Dih315glethyl-Z-hydroxypropylphosphonium 1o 1 e. XV Dicyclohexyl-Z-hydroxypropylphosphine.. Methyl bromide 1:1 Dicyclohexylmethyl-2-hydroxypropylphosphonium bromide. XVI Didodccyl-2-l1ydroxypropylphosphine Methyl iodide 1:1 Didodeoylmethyldrhydroxypropylphosphonium iodide. XVII..-" Diheptafiuoropropyl-Z-hydroxypropylphosdo 1:1 Diheptafluoropropylmethyl-Z-hydroxyp ne. propylphosphonium iodide. XVIII Bis(6-methoxy-2-r1aphthyl)-2-hydroxy- 1:1 Bis(G-methoxy-Z-naphthyl)methyl-2- propylphosphine. hydroxypropylphosphoniurn iodide. XIX Dipropyl-2-hydroxypropylphosphine Allylbrormde :1 Dipaogyl-Z-hydroxypropylphosphonium 1o 1 e. XX Bis(4-tolyl)-2-l1ydroxypropylphosphine Methyl iodide 0.5:1 Bisgi-tolyl)ingtlayl-Z-hydroxypropylphosp 01111111110 1 e. XXI Bis(4-chloropheny1)-2-hydroxypropy1phos- Butyl bromide 1:1 Bis(4chlorophenyl)butyl-2-hydroxypropylphine. phosphonium brom1de. XXII. Diphenyl-Z-hydroxypropylphosphine Ethyliodide 0.7:1 Diplhenylethy g-hydroxypropylphosp on1um1o 1 e. XXIII Bis[2-(trifluoromethyl)phenyH-ithydroxy- Methyl iodide 1:1 Bis[2-(trifluoromethyl)phenyl1methyl-2- propylphosphine. hydroxypropylphosphonium iodide. XXIV Dicyelopentyl-2-11ydroxypropylphosphine. Propyl iodide 1:1 Dieyclopentylpropyl-Z-hydroxypropylphosphonium iodide. I XXV Bis(4-tolyl)-2hydroxypropylphosphine Methyl iodide 0.3: Bis(4-tolyl)methyl-2-hydroxypropylphosphonium iodide. XXVI"; Diphenyl-1-(2-hydroxy)dodeeylphosphine do 1:1 Diphenylmethy1-1-(2-hydroxydodecyl)- phosphonium iodide. XXVII Bis(3-ethylphenyl)-2-hydroxyethylphos- .do 1:1 Bis(3-ethylphenyl)methyLZ-hydroxyethylphine. phosphomum iodide.

1 Diethylether.

2 Tetrahydrofuran.

3 As in Example I, supra, M is Li or Na.

the halide ions in this column originate from the inorganic halide byproduct realized upon the preparation oi RM where The phosphonium salts of the present invention repwherein R represents a member selected from the group resented by the formulae and R2PCH2CHR"Z have direct utility as flame retardants on cotton cloth. For example, a small but effective amount of the product of Example I, above, diphenylbis(2-hydroxypropyl)phosphonium bromide or methyldiphenyl-Z-hydroxypropylphosphonium iodide, may be dissolved in a suitable solvent, such as isopropyl alcohol (heating the alcohol enhances solubility), cotton cloth dipped into the resultconsisting of alkyl having from 1 to 12 carbon atoms, cycloalkyl, aryl, and substituted aryl, said substituents for aryl being selected from the group consisting of halogen, lower alkoxy, and trifluoromethyl; R represents a member selected from the group consisting of hydrogen, alkyl having from 1 to 12 carbon atoms and phenyl; and X represents a member selected from the group consisting of Cl, Br and I.

Diphenylbis(2 hydroxypropyl)phosphonium bro- 3. Dibutylbis(Z-hydroxybutyl)phosphonium chloride.

4;1 Dimethylbis 2-hydroxy-2-phenylethyl phosphonium iodi e.

5. Bis[3 (trifiuoromethyl)phenyl]bis(2 hydroxypro-' andhydr'olyzing' the product which results, thus producing the corresponding 2-hydroxyalkylphosphonium salt of the formula wherein R represents a member selected from the group consisting of alkyl having from 1 to 12 carbon atoms, cycloalkyl, aryl and substituted aryl, said substituents for aryl being selected from the group consisting of halogen, lower alkoxy and trifluoromethyl; R represents a member selected from the group consisting of hydrogen, alkyl having from 1 to 12 carbon atoms and phenyl; and M is selected from the group consisting of Li, Na and MgX, X being the same as above.

7. A method according to claim 6 wherein the product mixture resulting from hydrolysis is reacted with an organic halide of the formula RZ, wherein R" represents the organic moiety of a member selected from the group consisting of lower alkyl bromide, lower alkyl iodide, allyl chloride, allyl bromide, benzyl chloride, and benzyl bromide, and Z represents the halogen moiety, and recovering the corresponding Z-hydroxyalkylphosphonium salt of the formula R OH 69 A e RzPCHz HR Z wherein R and Z have the meaning given above.

8. A method according to claim 6 wherein the 2- hydroxyalkylphosphonium salt of the formula is recovered from the product mixture and the remaining product is reacted with an alkyl halide of the formula R"Z, wherein R" represents the organic moiety of a memher selected from the group consisting of lower alkyl bromide, lower alkyl iodide, allyl chloride, allyl bromide, benzyl chloride, and benzyl bromide, and Z represents the halogen moiety, and recovering the corresponding Z-hydroxyalkylphosphonium salt of the formula iziCHaHR"? wherein R" and Z have the meaning given above.

9. A method which comprises bringing into reactive contact, in the presence of an inert organic solvent, elemental phosphorus and phenyllithium in the presence of a bromide ion, reacting the resulting reaction product mixture with propylene oxide and hydrolyzing the product obtained in this last reaction, thus producing diphenylbis- (Z-hydroxypropyl phosphonium bromide.

10. The process according -to-claim 9 wherein the product remaining upon removal of diphenylbis(2- hydroxypropyl)phosphonium bromide is reacted with methyl iodide and methyl diphenyl-Z-hydroxypropylphosphonium iodide is produced.

11. The method according to claim 9 wherein the product mixture upon hydrolysis is reacted with methyl iodide and the product of this reaction, methyl diphenyl- 2-hydroxypropylphosphonium iodide is recovered.

No references cited. TOBI AS E. LEVOW, Primary Examiner. OSCAR R. VERTIZ, Examiner.

L. A. SEBASTIAN, Assistant Examiner. 

1. A 2-HYDROXYALKYLPHOSPHONIUM SALT OF THE FORMULA 